I used Rustolum on an old ford truck I once had. Not to harpoon the idea, but, problems started surfacing after about 1 yr. The problem is related to the fact that no hardner is used. I had paint pealing off in large areas, mostly on the top surfaces that get direct sun. It wasn't pretty.I also used mineral spirits to thin, but sprayed it on. Just one coat.

Why not do the same thing except with real automotive paint, perhaps single-stage enamel thinned down to really really thin? Would still be way less expensive than a pro job. Might be good enough for a beater.

I had to save that to my "Favoites" I just couldn't help it.
A couple of friends of mine and I painted a 1970 Camaro with rollers one night.The kid who owned the car,had afriend working at the local school bus terminal.He brought it in one night,and we all rolled it in school bus yellow.As a joke,the hood was done in flat black to match the busses.Only taped windows and chrome , but didn't remove anything . No sanding either , just rolled it , let it tack up , re-rolled it once more ,and unmasked and drove off still wet . It was fun , and the car was a real bondo box , with no sanding done to the bondo ahead of time either . By the next morning the car was dry , he came into the high school parking lot in the line of busses, and all we could do was laugh . I think it still cost him more than $50.00 and the car was horrendous .

Better off going to Maaco for the $300 paint job. Whatever he saved on the paint he paid for in time and effort. The rustoleum ain't gonna last long. The Maaco job looks pretty good for the money, especially if you do some of the prep work yourself.